Modern computers employ various forms of storage systems for storing programs and data. For example, various forms of disc drive systems have been designed to operate under the control of a computer to record information and/or retrieve recorded information on one or more recording discs. Such disc drives include hard disc drives which employ recording discs that have magnetizable (hard) recording material, optical disc drives which employ recording discs that have optically readable recording material, magneto-optical (MO) disc drives which employ recording discs that have optically readable magnetizable recording material, or the like.
Conventional disc drive systems typically include one or more recording discs supported for relatively high speed rotation on a rotary spindle. For example, FIG. 1 shows a side view of portions of a conventional disc drive system, including a conventional data storage or recording disc 200 supported on a spindle 210. A disc drive motor (not shown) is operatively coupled to the spindle 210 for rotation of the spindle 210 and the disc 200 supported thereon. A recording and/or reading head 220 is supported by suitable head support structure (not shown) adjacent the recording surface of the disc 200. To simplify the disclosure, FIG. 1 is shown with a single recording disc 200 having a single recording surface and a single head 220. However, other conventional disc drive systems employ multiple discs, double-sided discs (discs with recording surfaces on both surfaces) and multiple heads.
As shown in FIG. 1, the disc 200 has a central hub opening through which the spindle 210 extends. The disc 200 and spindle 210 are shown in a top view in FIG. 2. The spindle 200 extends through a central opening, which defines an inside diameter, of the disc. The disc 220 is secured at its inner diameter (ID), in a fixed relation with the spindle 210, and is supported such that the outer diameter (OD) portion of the disc 200 is free from contact with other components. In this regard, the disc 200 is clamped at its ID to the spindle 210 and is free at its OD. When the spindle 210 is rotatably driven, the disc 200 is caused to rotate with the spindle 210. A top (not shown) provides a protective cover for the disc 200.
Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings and spindle motor hub define a disc pack assembly.
The surfaces of the stacked discs are accessed by the read/write heads which are mounted on a complementary stack of arms which form a part of a head-arm assembly. Generally, the head-arm assembly has a body that pivots about a pivot mechanism disposed in a medial portion thereof. The body of the head arm assembly has a distal end on one side of the pivot mechanism and a proximal end on the opposite side of the pivot mechanism, adjacent the disk stack. The distal end of the body includes a pair of yokes 123, 125 (FIG. 4), on opposite sides of a coil 129. The head arm assembly selectively positions a proximal end of the body in response to positioning electronic signals applied to the coil. This positioning of the proximal end in cooperation with the pivot mechanism causes a distal end of the body, which supports the read/write heads, to move radially across the recording surfaces of the discs.
In this manner, the body of the head arm assembly may be moved in a pivotal motion to selectively position the head adjacent any recording location on the recording surface as the disc is rotated. Additionally, a yoke portion of the body of the head-arm assembly is aligned with a travel limiter stop, so as to contact the stop at one end of pivotal motion of the body.
In operation, the head 220 is moved in the radial direction to align or register with a desired track location on the recording surface of the disc. Once aligned or registered with the desired track location, the head 220 is operated to read or write information onto the recording surface at the desired track location. It is important to properly register the head 220 with the track location to effect accurate reading or writing operations on the registered track.
As stated above, when the head drive is not in use, the head is secured, or parked. As the head is easily damaged, care is required during the parking of the disc. In some conventional systems, once the servo-system is turned off, excess energy, or back emf pulses are used to move the head-arm assembly such that the head travels radially inward, toward the center of the disc for parking. As the head moves radially inward, the yoke end of the head-arm assembly swings radially outward until the head-arm assembly contacts the travel limiter.
One problem currently encountered during the parking of the head is that upon contact with the travel limiter, the yoke tends to bounce off of the travel limiter as there is no mechanism to grab the yoke and prevent it from moving. If the yoke bounces away from the travel limiter, the magnetic head then bounces back over the recording area of the disc. If the head-arm assembly continues to oscillate, the magnetic head is subjected to potentially violent movement back and forth across the disc which can cause damage to the head and/or result in head-disc contact in the recording area of the disc.
Attempts have been made to prevent the head from uncontrollable movement during parking. For instance, in one conventional system, a magnet device for providing a magnetic field between a pair of permanent magnets is added outside of the voice coil motor. In this system, a metal plate is added to the yoke that is nearest the added magnet device. The field that is created by the magnet device draws the metal plate on the yoke into the center of the magnetic field between the permanent magnets, such that the yoke, and therefore, the head, is substantially held in place. However, the additional magnet device located external to the voice coil motor can result in an increase in the cost of manufacturing, both in time and materials. Also, the use of an additional magnet device increases the number of components required to be contained in the disc drive housing and, thus, can require larger capacity housings or greater density and physical crowding of the disc drive system components in the housing. Also, because the additional magnet device creates a further magnetic field external to the voice coil motor structure, the additional magnet device can potentially cause interference with the magnetic storage of the storage discs.
In another system, a metal plate is attached to the yoke arm and a small cut is made in one of the conductive standoffs. The small cut allows for "loose" flux which attracts the metal plate. During parking, the metal plate is drawn by the loose flux to the conductive standoff and physically crashes into the conductive standoff thereby allowing metal to metal contact. As it is necessary to maintain a virtually clean environment inside the disc drive, metal to metal contact jeopardizes the cleanliness of the environment as particulate matter from the contacting metal can break loose and float within the disc drive housing.
As such, a need in the industry exists for a mechanism that allows for the securing or parking of the magnetic head in a controlled manner such that the possibility of the head uncontrollably oscillating is substantially eliminated. Further, a need exists for such a mechanism that minimizes any increase in manufacturing cost or complexity and is effective in maintaining a substantially contaminant free housing environment.